Question: The greatest integer function of $x$ is expressed as $[x]$ and is defined to be the greatest integer less than or equal to $x$. Find $[\pi - 4]$
Solution: Because $\pi$ is greater than $3$ but less than $4$,

$-1<\pi - 4<0$.  Therefore, $[\pi - 4]$ is $\boxed{-1}$